1. Field Of The Invention
The invention relates to a process for producing molded parts from flat tangled fiber fleece mats, preferably formed from binder-containing cellulose or lignocellulose fibers and to an apparatus for performing the process.
2. Description Of The Prior Art
Particular care is necessary when producing molded parts from tangled fiber fleece mats formed from binder-containing cellulose or lignocellulose fibers, because prior to shaping it is necessary to soften and make shapable, e.g., by vapor treatment, the fiber fleeces.
This significantly breaks down the fiber bond brought about by the binder, so that during the shaping process which takes place in the presence of the heat, there is a considerable risk of the fiber bond being broken and consequently in all cases the molded members would constitute waste.
It is known (German Pat. No. 2,338,650) to perform the shaping process in a press where a stepwise shaping takes place through the mold having a plurality of press rams in each case covering a deformation zone with a particular degree of deformation and which, independently of one another and in the sequence of the degrees of deformation, can be transferred from an open position into a pressing position. Apart from the costly construction of the press and the long and costly process, it is necessary to pre-compress the fiber mat at those points where a very considerable final deformation takes place. Therefore, of late, the procedure has been to finally shape the heat-softened fiber mat by press tools which can be moved against one another, initially by premolding and then by final molding. As is known, this is carried out by two separate molds, one of which carries out the premolding and the other the final molding. The fiber mat is removed from a stack and placed on a premold after being softened in a heating station and brought to a temperature adequate for shaping purposes. The premold comprises a press equipped in a known manner with a female mold and a male mold, whose shaping surfaces are designed in such a way that the heated, softened fiber mat can satisfactorily follow the shaping. Following preshaping, the preshaped part must cool in the premold in order to be removed therefrom and be placed in the second press used for final molding. The second press also comprises a male mold and a female mold where the premolded part which has cooled in the meantime must be heated again, so that final molding between the two hot press tools can again be performed on an adequately softened premolded part.
Another process for producing molded parts is known (DOS No.2,615,793) in which between two suitable press tools in a first press stroke a binder-containing fiber mat, e.g., of cellulose, or lignocellulose material, is compressed into a molded part serving as a supporting layer, which is left in the press tool and after introducing a decorative surface layer is permanently joined therewith over its entire surface area in a further press stroke.
This is based on the fact that molded parts of the present type when used as decorative elements, linings and also supporting parts, e.g., for lining vehicle interiors, must undergo surface finishing after producing the actual supporting layer. The problem of the aforementioned prior art is based on supporting layers of laminates, laminated wood, pressed wood fiber materials and and like and is only concerned with the fact that after producing molded articles from these materials, there must be a surface coating with a needled fleece. Such a molded article is produced by initially compressing the supporting layer and after obtaining the corresponding molded article the decorative and visible side thereof is previously coated with a thermally acting adhesive and then the needled fleece is applied. Under substantially constant temperature conditions in the same press a second press stroke follows for which, however, the compression molding pressure is considerably reduced to prevent damage to the needled fleece.
The conditions are similar in a further known process for producing a shaped lining sheet formed from a corrugated paper or board support and in which the covering layer is pressed on by means of a cushion insert which can be introduced into the press (DOS No. 2,731,691).
The pressing on of the needled fleece according to the aforementioned process with the same press tool as used for producing the molded article, i.e., with unchanged contours of the press ram, does not take into account the locally differing tensile and compressive stresses and consequently changes in the overall thickness as is the case with the last-mentioned known process. Thus, only inadequately compressible needled fleeces can be used for the process, whose structure and appearance do not significantly change due to the compression process. However, satisfactory results are not obtained through the known use of a cushion insert in the form of an air cushion, particularly in the case of complicated three-dimensional shapes, e.g., with vertical or sharply bent edges.
The known processes can in particular not be used on those decorative layers unable to withstand high molding temperatures of 150.degree. C. to 200.degree. C. or possibly even higher, whose structure and appearance suffers through the contour of the moved press tool halves and in which the adhesive layer or adhesive used would pass through the layer during pressure application.
The number of stages necessary constitutes a disadvantage of all the known processes. These stages involve the transfer of the individual fiber mats to a heating station, the manual removal of the heated fiber mats from the heating device and the introduction thereof into the premold, the performance of the premolding process, the cooling of the premolded part to a transportable solidified state, the removal from the premold and the introduction into the final mold and the separate performance of the final molding of the intermediate produce, whilst applying the decorative layer. The requisite large number of process stages leads to high labor costs and particularly is very time-consuming. Another disadvantage is that the fibrous material must be heated a number of times, which disadvantageously influences the characteristics of the binder.
The problem of the invention is to eliminate the disadvantage of the prior art and to provide a process and apparatus such that, whilst significantly reducing the necessary number of process stages, the premolding and final molding can take place in the same heat, i.e., without any intermediate cooling of the tangled fiber fleece mat. In addition, it permits the application of decorative surface layers from substantially random materials, even in the case of the most complicated shapes.
This problem is solved by a process according to the preamble of the main claim by means of features given in characterizing part thereof. The subclaims relate to advantageous further developments of the invention.